Its comparatively much more open, with interface and protocols specified and open source firmware implementations widely used in the wild. I'm also including BIOs/UEFI in this.

ARM and phone manufacturing is a hot mess in comparison. We're still trying to reverse engineer M series MacBooks and iPhones are off limits. Android is also not open source, no AOSP does not count.

There would be a lot more competition in the space if the hardware had proper specs, like x86 does.